- Replaced GeomAPI_PointsToBSpline with GeomAPI_Interpolate to create the default "splines" with the OCC kernel. This automatically creates C2 continuous BSplines, and also works in the periodic case.
- Added full interface to BSpline creation with specification of degree, weights, knots and multiplicities. Seems OK for the non-periodic case; periodic case is still TODO.

Added new option Geometry.OCCTargetUnit to choose the target unit length when importing step and iges files.
Set it to meter ("M") by default.
Warning: this changes the old behavior, which was to convert in millimeters (the OpenCASCADE default).